I'm curious that she is wetting her blanket. That was not a problem our Tessa had. Not sure if it means anything or not. What I'd be concerned about is a urinary tract infection. If she does not start to be able to hold her bladder soon, I'd be talking to my vet about that possibility. It may still be more about the anesthesia drugs still, causing her not to have total control over the sphincter muscles. Perhaps you might put a white sheet under her so you can examine the color of the urine. Light yellow is good, dark yellow or blood tinged would be a reason to call the vet sooner rather than later. Also, if the urine is strong smelling that can mean infection.
Yes, Tessa was very sleepy for several days. The surgery really takes it out of them and healing is exhausting. I'd just advise not doing anything else with her but outside to potty, and back to bed. Soon enough, if things go well, you'll have trouble keeping her from over-doing, so enjoy this time when she is willing to sleep. Sleep is what she needs for sure.
As far as food, now is the time when spoiling her is OK. I'd go for easy to digest food such as boiled chicken(boneless), mixed with cooked white rice, half and half. A bit of scrambled or hard cooked egg can be good, as well as plain, unsweetened yogurt. I'd stay away from kibble (what I think you call "biscuit" over there
) for a while, as that is harder to digest, and also quite dehydrating, and also not load up on commercial dog treats, as those tend to be sort of doggy junk food. A good quality canned meat dog food might also be appetizing for her, and should be easier to digest than dry kibble . Her tummy is likely to be sensitive now, and her appetite low from the drugs, but if you can get some nutrition in her, that will help her to heal. And just as, or even more essential, is to get her hydration up. A dilute chicken broth might be tempting. You can use the water you boil the chicken in. Offer her sips frequently.
I'm really surprised your lab took the spay so easily, especially as a mature dog who had, had puppies. A hysterectomy for us females is major surgery. I think what you are seeing with Daisy is not unusual, and certainly what happened with our Tessa. She was low for quite a few days and I was pretty worried!
Anyway, those are some of the things I've learned and just wanted to pass on to you! Best wishes!